
Of course our California grass carp only get to 40 pounds.
This is because they are all triploids (created by damaging the eggs immediately upon fertilization). Triploids only reach about half the weight of diploids and live only half as long, but they eat about 90% as much as diploids eat. They have the advantage that they are sterile, since the California agriculture folks are very sensitive about alien lifeforms reproducing here.